In my comparison between the Leo II and Janus D, I noted the Janus D's superior separation, because the individual notes were more tightly outlined and compact. And, the latter had a more expansive background. So, although instruments were placed just as close as they were on the Leo II, you could feel more space behind them, so they felt more three-dimensional and resolved as they decayed. The Leo II is more transparent and resolving than the 8-wire Ares II, but as modestly as the latter performs in those regards, there's still an effortless that the Leo II just barely loses out on. Whether or not that last bit of headroom is worth the loss in transparency, resolution and ergonomics is of course up to the user. But if that's the discussion, it's also worth keeping in mind the Bespoke Ares II's tonal differences as well.
As I said to Eric when I tried the Leo II for the first time, it's one of the most 8-wire-like 4-wire cables I've tried, with the only contenders being PWAudio's 2-wire (4-conductor) 1960s and probably the Horus. If you want the best compromise between 4-wire ergonomics and 8-wire performance, and you're good with the Leo II's signature, then it's a great buy IMO.